Modes of area searching and exploratory behaviour of the sympatric pine marten, Martes martes (L., 1758), and stone marten, Martes foina (Erxleben, 1777), were studied by snow-tracking in two regions of Poland. The accuracy of identifications of the two species on the basis of their snow tracks was assessed by DNA analysis of their faeces, as collected on the tracks; identifications were found to be correct in 88% of cases. Although most activities of the two species were concentrated on the forest floor, pine martens climbed trees, moved in tree crowns, and searched the bases of tree trunks and tree hollows more frequently than stone martens. In contrast, stone martens were more inclined to search for food in brushwood and piles of wood, and visited logged areas and garbage dumps more frequently. Pine martens avoided man-made objects and barriers such as roads and passed through open areas with reluctance. Such behavioural traits make this species particularly vulnerable to forest fragmentation and human activity in forests. Stone martens often explored woodless areas and inhabited buildings, which allowed them to use habitats substantially transformed and intensively explored by humans. The future coexistence and relative numbers of the two martens in forest habitats will depend on the mode of forest management and on the existence of effective migratory corridors connecting forest patches.